[OZAPRS] APRS 'idea' ? - needs some clarification

Tue Feb 12 12:33:38 EST 2013

Ben,
I don't think it could be better said... Well done.

73's,

Rob Heyer          ( VK2XIC )

APRS
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VK2XIC-2 Experimental (TT4)
VK2XIC-3 Camp Site
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VK2XIC-5 On Bicycle

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http://aprs.fi/?call=vk2xic-9&mt=roadmap&z=11&timerange=3600

VK2RMP - IRLP  Node No. 6018 (146.850 MHz)
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                  IARS
                  SES Shellharbour City (NSW)

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1 Corinthians 16 vs 13 - 14

________________________________
 From: Ben VK2BEN <ben at vk2ben.com>
To: ozaprs at aprs.net.au 
Sent: Saturday, 2 February 2013 12:32 PM
Subject: [OZAPRS] APRS 'idea' ? - needs some clarification

HI Paul,

I think there is a profound question in your message below, but some clarification is required to give you a satisfactory answer.

After rephrasing your entire question in a couple of different ways here in my head, I think I may have deduced what you might be asking:

Are you suggesting that, instead of multiple stations (by which you might mean "digipeaters"?) re-transmitting all APRS packets that it hears over the air, or gathers from an Internet Gateway ("iGate") in a given area; that only "one" station should do this and cover a really large geographical area?

Well, actually that how digipeaters work in any case, so I am still not sure that I fully understand your proposal from the start. Digi's will re-transmit what they hear - within the limits set by their Wide-n parameters - and IS (Internet) to RF (Radio) gateways (iGate) are generally not encouraged [perhaps even strongly discouraged? I am open to correction here]  due to the massive amount of data with which they could potentially flood the RF channel.

Digi's are strategically placed to cover large areas [and to stretch the VHF network out to sparsely populated areas and even link such scattered areas back to the network if there are no Internet links at the regional areas]  and to repeat APRS posits to mobile and fixed users of that network who may not have received the originating signal (which is usually a lower-powered mobile transmitter with limited LoS range). Fill-in Digi's are set up in blind spots, or as links between service areas, that might not be covered by the regional Digipeater. These can be given limited range (path, as well as RF power) so as not to fill the channel with redundant data. Thus, I think that the short answer is no; we cannot realistically remove large numbers of Digipeaters in order to reduce traffic on the APRS channel. It would not solve many problems. Especially here in Australia, where the frequency can hardly be described as 'overloaded' ;-)

As for reducing the amount of traffic on the frequency in a given geographical region; this would become a moot point because the same amount of APRS data would still need to be transmitted to service that area all at once with a single transmission. But instead of several short bursts of repeated data coming from a group of well-managed digipeater sites, it sounds like we might end up with really long (and perhaps more susceptible to interference and errors?) transmissions carrying all sorts of position data that might not be wholly relevant to the users in that specific area. Currently, Digi's are dispersed so as not to cover the same areas as each other, nor with too much overlap. At the same time, protocols are in place (within the TNCs) to disallow indiscriminate repeating of data and thus unending loops of repeated data.

I think there is a fine balance between covering all areas well with as few digipeaters as possible, whilst at the same time filling in valleys and great open spaces with the required positioning data. The way the system works right now is pretty darned good. And after reading thru parts of the aprs.org website, I am surprised that anybody can understand it at all :-P

Paul, I apologize if I have extrapolated far more from your brief proposal than you might have intended, but it seemed necessary to clarify a few things before approaching what you appeared to be asking. Hopefully I didn't veer off the track too far?

73,
Ben vk2ben

>> Hi there all,
>> Its been a while from my last post, I have an idea. I have no idea if this
>> has been implemented anywhere in the world but this idea could be done.
>> 
>> I have been thinking about the way that the APRS network works, now I might
>> be wrong with fully understanding the network but this is my idea.
>> 
>> All the sites are Receive getting data from the mobiles and passing it on to
>> a main internet link as per normal and the remote sites passing the
>> information as per normal.
>> The main difference is with a single area transmitter what gathers data and
>> what is coming from the internet is transmitted from a single site.
>> Of course as you move away from possible single site receiving maybe another
>> site could pick up the slack with another internet to RF gateway, there
>> might be another way of doing it, this I feel could reduce the traffic by
>> 25% - 33%.
>> 
>> Cheers and 73s'
>> Paul
>> 
>> VK5VCO
>> 
>> 
>> *****************************

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